Projection display providing additional modulation and related methods

ABSTRACT

A projection display system includes a spatial modulator that is controlled to compensate for flare in a lens of the projector. The spatial modulator increases achievable intra-frame contrast and facilitates increased peak luminance without unacceptable black levels. Some embodiments provide 3D projection systems in which the spatial modulator is combined with a polarization control panel.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/452,562, filed Mar. 7, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/950,010, filed Nov. 24, 2015, now U.S. Pat. No.9,626,921, which is a continuation of U.S. patent application Ser. No.13/409,425, filed Mar. 1, 2012, now U.S. Pat. No. 9,224,320, whichclaims priority from Provisional Application No. 61/450,750, filed Mar.9, 2011, all of which are incorporated by references in their entirety.

TECHNICAL FIELD

This invention relates to displays. The invention relates specificallyto projection displays in which projectors project images onto screensfor viewing.

BACKGROUND

Most digital projector systems (DLP, LCOS) have low intra-frame contrastratios on the order of 100:1 when imaging a reflective screen. This ismostly due to flare in the optics (lenses), which scatters light andhence reduces contrast. The human visual system is capable ofappreciating closer to 10,000:1 intra-frame contrast ratios, so there isvast room for improvement in digital projection technology.

Furthermore, the peak luminance of digital projectors is often limitedto undesirably low levels (e.g. 50 cd/m²) since, due to the low contrastratios, black levels would be raised objectionably if maximum luminancewere increased. For example, with a peak luminance of 50 cd/m² at acontrast ratio of 100:1, the black levels are 0.5 cd/m². If theprojector peak luminance were increased to 500 cd/m², the black levelswould rise to 5 cd/m², which viewers would perceive as distinctly grey.

Some displays are 3D displays capable of providing separate images forviewing by viewers' left and right eyes. Maintaining brightness in 3Ddisplays is a particular problem since the polarizers, filters and/orshutters used to control which eye can see each image tend to absorb atleast some light.

There is a need for projection display systems capable of improvedintra-frame contrast. Included in such need is a need for more effective3D projection display systems.

SUMMARY

This invention has a range of aspects. One aspect provides projectiondisplay systems that incorporate spatial modulators between a projectorlens and a screen. The screen is a reflective screen in someembodiments. Another aspect provides methods for controlling aprojection display system which methods comprise controlling thetransmissivity of regions in a spatial modulator to compensate for lensflare in a projection lens of the projection display system. Anotheraspect provides a controller for a projection display system that isconfigured to control the transmissivity of regions in a spatialmodulator to compensate for lens flare in a projection lens of theprojection display system. In some embodiments the projection displaysystem is a polarizing type 3D display system comprising a polarizationcontrol panel. In some embodiments the polarization control panel andspatial modulator are integrated in a single unit.

An example aspect provides a projection display system comprising aprojector comprising a projection lens arranged to focus an image fromthe projector onto a screen, a spatial modulator is disposed between theprojection lens and the screen. A controller is connected to controltransmissivity of a plurality of regions of the spatial modulator baseddirectly or indirectly on image data.

Further aspects of the invention and features of a variety ofnon-limiting example embodiments are described below and illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate non-limiting example embodiments.

FIG. 1 is a schematic illustration of a projection display systemaccording to an example embodiment.

FIG. 2 is a block diagram of an example control system.

FIG. 3 is a block diagram of another example control system.

FIG. 4 is a schematic illustration of a 3D projection display systemaccording to another example embodiment.

DESCRIPTION

Throughout the following description specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

Providing a projection display having an increased contrast ratio canallow higher peak luminances without raising the black levels, and henceprovide a better viewing experience.

FIG. 1 illustrates a projection system 10 according to a first exampleembodiment. System 10 comprises an image projector 12. Image projector12 receives image data at an input 14 and projects light modulatedaccording to the image data through a lens 16 for display on a screen18. A viewer V can observe light that has interacted with screen 18.Screen 18 may comprise a reflective screen or a transmissive screen, forexample. Some embodiments provide front-projection projector systems andsome embodiments provide rear-projection projector systems. Theillustrated embodiments shows a front-projection projector system.

A spatial light modulator 20 is provided between lens 16 and screen 18.Spatial light modulator 20 is operable to control the transmission oflight from lens 16 to screen 18. Spatial light modulator 20 can becontrolled so that different portions of spatial light modulator 20transmit different proportions of the light incident thereon to screen18. In some embodiments, spatial light modulator 20 comprises a numberof distinct regions and a transmissivity of each of the regions isindependently controllable. The regions may be arranged in an array andmay comprise an array of cells or pixels, for example.

Spatial light modulator 20 may be of high or low resolution. Boundariesbetween different controllable regions may be sharp but in someembodiments the boundaries between adjacent controllable regions areblurred (e.g. the regions may overlap such that changes intransmissivity between adjacent regions occurs in a number of steps or asmooth continuum). Spatial light modulator 20 may be monochrome orcolor.

Spatial light modulator 20 may be located at a position such that theeffect of any of its controllable regions is blurred at screen 18. Theideal distance between lens 16 and spatial modulator 20 is a function ofthe optics, particularly the aperture and focal length of lens 16 aswell as the distance to and size of the screen 18. The blurring arisingfrom the fact that spatial modulator 20 is not in a plane where theimage being projected onto screen 18 is in focus helps make thecontrollable elements of spatial modulator 20 imperceptible to viewer Vwhile allowing some local control over image brightness.

For many applications it is sufficient for spatial modulator 20 toprovide low-resolution control over the brightness of an image on screen18. Such low-resolution control can be sufficient to make large darkregions on screen 18 blacker than they could otherwise be due to lensflare and other effects.

Since spatial modulator 20 is between lens 16 and screen 18 rather thanupstream from lens 16, spatial modulator can be used to compensate forscattering in lens 16 to at least some degree.

In some embodiments, spatial light modulator 20 has the property that itis capable of transmitting a relatively large portion of the lightincident from projector 12 to screen 18. In some embodiments, atransmission coefficient T is given by:

$\begin{matrix}{T = \frac{I_{T}}{I_{I}}} & (1)\end{matrix}$where I_(I) is the intensity of light incident on spatial lightmodulator 20 and I_(T) is the intensity of light that is passed byspatial light modulator 20. In general T can be made to vary on aregion-by-region basis (e.g. a pixel-by-pixel basis) by supplyingappropriate control signals to spatial light modulator 20. In suchembodiments, the maximum transmission coefficient T_(MAX) may representthe maximum value of T for any allowed control signals (i.e. spatiallight modulator 20 may pass up to T_(MAX) of the light incident on it toscreen 18). In some embodiments, T_(MAX) exceeds ½. In some embodiments,T_(MAX) exceeds 0.85 (i.e. in such embodiments spatial light modulator20 may pass up to 85% or more of the light incident on it to screen 18).

Not all spatial light modulator technologies have the property ofproviding relatively large values for T_(MAX). Spatial light modulatortechnologies that can provide values of T_(MAX) well in excess of ½include electrowetting (EW) modulators, dye-doped polymer-stabilizedcholesteric texture (“PSCT”) modulators, high-transmissivity lightvalves and some low-contrast liquid crystal displays.

In some embodiments spatial light modulator 20 comprises anelectro-wetting modulator. In some embodiments spatial light modulator20 comprises a dye-doped PSCT modulator. In some embodiments spatiallight modulator 20 comprises another type of spatial light modulatorhaving T_(MAX) in excess of ½ such as a suitable liquid crystalmodulator, a suitable array of optical valves or the like. One advantageof electro-wetting modulators is that such modulators do not requirepolarized light (as in the case of LCD modulators).

Where spatial modulator 20 is an LCD modulator or a modulator of anothertype that only passes polarized light then, for maximum opticalefficiency, it is desirable that projector 16 be of a type that emitspolarized light (for example, projector 16 may comprise an LCOSprojector or may comprise a reflective polarizer in its optical path),or some means should be provided for recycling light that is notpolarized in such a manner that it can pass through spatial modulator20.

In some embodiments, the controllable regions of spatial light modulator20 are larger than the resolution of projector 12 (i.e. projector 12 hasan overall image resolution that is greater than that of spatialmodulator 20).

The overall intra-frame contrast achievable by projection system 10 canbe estimated by multiplying the native contrasts of projector 12 andspatial modulator 20. For example, where projector 12 has a contrastratio of 100:1, and spatial modulator 20 has a contrast ratio of 100:1the contrast ratio of projection system 10 can be as much as 10,000:1.The full contrast may not be achievable for all image content based onrequirements of temporal stability and artifact minimization duringmotion sequences, depending largely of the difference of resolutionsbetween projector 12 and spatial modulator 20.

In some cases, spatial light modulator 20 has a significantly smallercontrast ratio than does projector 12. For example, spatial lightmodulator 20 may comprise a transmissive panel having a contrast ratioof less than 100:1. For example, spatial light modulator 20 may have acontrast ratio of 15:1 or 10:1 or 2:1 in some embodiments. Even suchsmall contrast ratios can be sufficient to provide meaningfulimprovements in the contrast ration of projection system 10, thusfacilitating, inter alia greater maximum luminance without unacceptablyhigh black levels.

Even in embodiments where spatial light modulator 20 has a relativelysmall contrast ratio, the effect of spatial light modulator 20 on theoverall contrast ratio of projection system 10 may be quite significant.For example, consider the case where projector 12 has an intra-framecontrast ratio of 100:1 and spatial light modulator 20 has a contrastratio of only 15:1. The contrast ratio of the overall projection system10 may be as great as 1500:1 (achieved by suitably controlling both theimage projected by projector 12 and the transmissivity of regions ofspatial light modulator 20.

In some embodiments, spatial light modulator 20 is operated as asubstantially transparent window which is darkened in specific regionsto depress the luminance in the selected regions. The selected regionsmay, for example correspond to dark or black parts of the image so thatthe effect of darkening regions of spatial modulator 20 is to depressthe black level of projection system 10.

In the illustrated embodiment, spatial modulator 20 is located afterlens 16. Thus, spatial modulator 20 may be used to compensate for flarein lens 16. FIG. 2 is a block diagram that illustrates one embodiment ofa control system 30 for a projection system like projection system 10.Control system 30 receives image data 32 to be displayed. Image data 32may, for example, comprise a still image, a file containing a videosequence, a video stream, an output from a graphics adapter or a mediaplayer or the like.

Image data 32 (after being decoded, if necessary, and after any desiredpreliminary image processing) is provided to drive projector 12 and alsoto a projector simulation 34. Projector simulation 34 computes anestimate 35 of the light that projector 10 will emit in response to theinput of image data 32. In some embodiments, the estimate is determinedin real-time on a frame-by frame basis. In some embodiments the estimateis determined for each frame. In some embodiments, the estimate isdetermined for a group of frames having similar image content. Theestimate produced by projector simulation 34 may, for example, comprisea map of estimated luminance as a function of position. In someembodiments the estimate produced by projector simulation 34 is a maphaving the resolution of spatial modulator 20. This may be significantlylower than the resolution of the images projected by projector 12.

In some embodiments, projector simulation 34 applies methods andapparatus as described in PCT international application publication No.WO 2006/010244 entitled RAPID IMAGE RENDERING ON DUAL-MODULATOR DISPLAYSwhich is hereby incorporated herein by reference.

Projector simulation 34 applies a mathematical model of projector 12including lens 16. The model preferably takes into account flare in lens16. In some embodiments, the model determines the luminance of pixels ofprojector 12 when displaying an image as specified by image data 32,applies a point spread function to estimate spread of the light from thepixels at lens 16 and applies a model of lens 16 which includesscattering within lens 16 to estimate a distribution of light at spatialmodulator 20 from the pixel in question. Application of the point spreadfunction and the lens model may be performed separately or in a combinedcalculation. The amount of light incident at each pixel of an observableimage projected onto screen 18 can then be estimated by summingcontributions from the pixels of projector 16.

In some embodiments, projector simulation 34 operates by applying thepoint spread function and lens model to groups of pixels of projector12. In such embodiments, projector simulation 34 may calculate anaverage luminance of a group of pixels of projector 12 (e.g. a set ofpixels that will illuminate a small region on screen 18). One way toachieve this is to apply a model of the light source component ofprojector 12 to the values in image data 32 to yield an estimate of theluminance produced by pixels within projector 12, downsample the result,and apply the point spread function and lens model to the pixels of thedownsampled result.

Projector simulation 34 may comprise filtering the input signal (imagedata 32) with a point spread function measured from projector 12 tosimulate the resulting loss of contrast. The point spread function maybe measured, for example, by turning on one pixel or group of pixels inprojector 12 and measuring a distribution of light produced by the onepixel or group of pixels at screen 18 or at another plane or surfacebetween lens 16 and screen 18. The point spread function indicates howlight from one pixel or group of pixels of projector 12 becomesdistributed as the light propagates through projector 12 including lens16.

A correction system 36 compares the estimate prepared by projectorsimulation 34 to image data 32 and determines a correction to be appliedby varying the transmissivities of controllable regions of spatialmodulator 20. A correction factor may be determined, for example, bydividing the input image data by the estimate produced by projectorsimulation 34 (or multiplying by the reciprocal of the estimate producedby projector simulation 34). In areas where estimate 35 indicates alight level higher than that specified in the input image data thecorrection factor will be less than 1.0. A correction signal based onthe correction factors determined by correction system 36 is connectedto drive spatial modulator 20. For the regions in which the correctionfactor is less than 1.0, spatial modulator 20 is controlled to decreasethe light passing to screen 18 by the indicated amount. For regionswhere the correction factor is 1.0 or more, the corresponding region(s)of spatial modulator 20 may be controlled to remain in their most highlytransmissive (e.g. most transparent) states.

In some embodiments the control method is iterative. An optionalcorrection system 36A modifies the image data delivered to projector 12based on the estimate prepared by projector simulation 34, a model ofthe behavior of spatial modulator 20, the control signals drivingspatial modulator 20 and image data 32. The adjustment may, for example,be determined by comparing image data 32 to an estimate of the imagethat would be displayed on screen 18 as a result of the modification ofthe light from projector 12 by spatial modulator 20. The image datadriving projector 12 may be modified by correction system 36A so as toincrease the brightness of pixels that are estimated to be dimmer thanspecified in the image data and to decrease the brightness of pixelsthat are estimated to be brighter than specified in the image data. Insome embodiments modifications to image data driving projector 12 andcontrol signals for spatial modulator 20 are refined over a number ofsuccessive iterations to provide improved compensation for flare in lens16 and/or other imaging defects introduced by imperfections in theoptical path to screen 18.

A control system may take into account a model of the component of lensflare which provides a general scattering that floods the whole screen18 with scattered light. By shading regions of the projected image thatare darker than the rest, the control system can reduce this scatteredlight. By doing so, the intensity of the light that is intended to beprojected by projector 12 in darker areas of the image is also reduced.This can be compensated for by modifying image data 32 to increase theintensity of the image data corresponding to darker parts of the imageto compensate for the dimming provided by spatial modulator 20.

An alternative control arrangement 30A is illustrated in FIG. 3. Controlarrangement 30A operates by determining driving values for spatialmodulator 20 and then determining modified image data for drivingprojector 12. The modified image data takes into account the varyingtransmissivity of spatial modulator 20. In control system 30A, imagedata 32 is provided as an input to a spatial modulator driver 40.Spatial modulator driver 40 determines driving signals for spatialmodulator 20 based on image data 32. For example spatial modulatordriver 40 may extract or calculate a monochrome (luminance) version ofimage data 32.

The luminance image may be downsampled to a resolution matching that ofspatial modulator 20. Driving signals 41 for elements of spatialmodulator 20 may be arrived at in various ways such as: taking aweighted summation of input values; calculating a weighted combinationof maximum and mean of each region of an image; downsampling the image;and the like. Preparing driving signals 41 may comprise smoothing imagedata 32 by applying a filter kernel (Gaussian or otherwise).

Driving signals 41 are also provided to a modulator simulation 44 whichcomprises a model of the effect of spatial modulator 20 on light fromprojector 12. Modulator simulation 44 may provide as an output a map 45that specifies how much of the light generated by projector 12 for eachimage pixel is estimated to reach screen 18 for the case where spatialmodulator 20 is driven by driving signals 41. In this case, modulatorsimulation 44 may comprise a model of spatial modulator 20 and a pointspread function that describes the spreading of light from pixels ofprojector 12 as that light passes through projector 12 including lens 16and spatial modulator 20 to screen 18.

Correction system 36A then divides image data 32 by the correspondingvalues in map 45 to obtain modified image data 32A for driving projector12 to achieve an improved display of the image(s) of image data 32 onscreen 18.

A control arrangement like arrangement 30A may also be configured todetermine driving signals 41 and modified image data 32A iterativelythrough two or more iterations.

In some embodiments, a control system operates by passing image data 32through a filter that simulates the blur of the optical system ofprojector 12 (including lens 16). The filter may be designed based onmeasurements of test patterns projected by projector 12 or estimatedbased on the design of projector 12 and lens 16. The filtered imagerepresents the flare that it is desired to remove. The flare may beremoved by one or both of subtracting the predicted flare (or thepredicted flare multiplied by a weighting factor) from the input imageand increasing the absorption of parts of spatial modulator 20 thatcorrespond to darker regions of the image while increasing the intensityof the image data in those darker regions to compensate for the effectof spatial modulator 20. The change to the image data affects thepredicted flare. Consequently the process may be iterated untilsufficient compensation for flare in lens 16 has been achieved.

In an alternative control arrangement, modified image data 32A anddriving signals 41 are each derived directly from image data 32. Forexample, driving signals 41 may be determined by downsampling and/orfiltering image data 32, identifying high-brightness areas in image data32 having an average brightness exceeding a threshold and settingcontrol signals 41 to cause spatial modulator 20 to dim areassurrounding the high brightness areas according to a dimming function.Modified image data 32A may be generated by boosting slightly the pixelvalues (or boosting the brightest pixel values or pixel values exceedinga threshold) for pixels in areas outside of the high-brightness areas.

In an alternative control arrangement, modified image data 32A anddriving signals 41 are each initially derived directly from image data32 and are then iteratively refined as described above, for example.

Lens 16 may be adjustable. For example, lens 16 may comprise a zoom lensor a lens that provides adjustment for barrel distortions or the like.In such case the setting of the lens will affect lens flare and othercharacteristics of the point spread function for light passing throughlens 16. Where lens 16 is adjustable, a projector simulator 34 or amodulator simulator 44 may be configured for a specific setting of lens16. For example, lens 16 may be adjusted to a desired setting and then acalibration may be performed. Performing the calibration may comprise,for example, projecting light using a pixel or a small group of pixelsof projector 12 and monitoring the resulting distribution of light atscreen 18 or spatial modulator 20 or another convenient surface.Calibration information based on the resulting distribution of light maythen be used to configure projector simulator 34 or modulator simulator44.

In other embodiments, a control system contains calibration informationfor multiple settings of lens 16 and receives a signal indicative of azoom level and/or one or more other settings of lens 16. Based on thesignal the control system selects an appropriate set of calibrationinformation and applies that calibration information in controllingprojector 12 and/or spatial modulator 16.

An advantage of some embodiments is that projector 12 may comprise anysuitable projector. For example, projector 12 may be any commerciallyavailable projector that is suited for the intended application. Suchprojectors 12 may be used with no modifications in some embodiments. Aretrofit system may comprise, for example a control box having a firstconnector for connecting an incoming video signal carrying video data 32to be displayed and a second connector for connecting to a video inputof a projector 12 and a spatial modulator 20 connectable to becontrolled by the control box. The retrofit system may be set up byfinding an optimal placement for spatial modulator 20 (i.e. a locationsuch that modulator 20 is close enough to lens 16 to modulate light overthe entire screen 18 and is close enough to screen 18 to provideadequate local control of brightness. The control box may then beconfigured to control spatial modulator 20 to compensate for flare inlens 16 in a tuning or calibration step.

Control systems 30 and 30A may be implemented in hardware, software(including ‘firmware’) or suitable combinations of hardware andsoftware. Certain implementations of the invention comprise computerprocessors which execute software instructions which cause theprocessors to perform a method of the invention. For example, one ormore processors in a projection system may perform methods as describedabove for generating driving signals for a spatial modulator 20 and aprojector 12 by executing software instructions in a program memoryaccessible to the processors that manipulate image data and models ofthe optical system of the projector and/or spatial modulator. Forexample, such image processing may be performed by a data processor(such as one or more microprocessors, graphics processors, digitalsignal processors or the like) executing software and/or firmwareinstructions which cause the data processor to implement methods asdescribed herein. The software and other modules described herein may beexecuted by a general-purpose computer, e.g., a server computer orpersonal computer. Furthermore, aspects of the system can be embodied ina special purpose computer or data processor that is specificallyprogrammed, configured, or constructed to perform methods as explainedherein.

Instead or in addition to programmable data processors, control systems30 and 30A may comprise logic circuits which may be hard configured orconfigurable (such as, for example logic circuits provided by afield-programmable gate array “FPGA”).

The invention may also be provided in the form of a program product. Theprogram product may comprise any non-transitory medium which carries aset of computer-readable signals comprising instructions which, whenexecuted by a data processor, cause the data processor to execute amethod of the invention. Program products according to the invention maybe in any of a wide variety of forms. The program product may comprise,for example, media such as magnetic data storage media including floppydiskettes, hard disk drives, optical data storage media including CDROMs, DVDs, electronic data storage media including ROMs, flash RAM,hardwired or preprogrammed chips (e.g., EEPROM semiconductor chips),nanotechnology memory, or the like. The computer-readable signals on theprogram product may optionally be compressed or encrypted. Computerinstructions, data structures, and other data used in the practice ofthe technology may be distributed over the Internet or over othernetworks (including wireless networks), on a propagated signal on apropagation medium (e.g., an electromagnetic wave(s), a sound wave,etc.) over a period of time, or they may be provided on any analog ordigital network (packet switched, circuit switched, or other scheme).

One application to which the invention may be applied to advantage isproviding projection systems for use in projecting 3D images. Suchsystems may include a polarization control panel that can be controlledto create a 3D image by sequentially switching the polarization betweentwo orthogonal polarizations associated with corresponding lenses of aviewer's glasses. In such a system different images may be displayed toa viewer's right and left eyes creating a stereoscopic effect. Anexample polarization control panel is described in US2011/032345A1 whichis hereby incorporated herein by reference. Suitable polarizationcontrol panels are commercially produced by RealID Inc. of BeverlyHills, Calif., United States of America.

FIG. 4 shows an example projection system 10A according to an embodimentwhich includes a polarization control panel 50 capable of switchingpolarization between two states corresponding to images for viewingrespectively by viewers' left and right eyes. A controller (not shown inFIG. 4) controls projector 12 to project left and right images forviewing by viewers' left and right eyes in alternation and to switch thepolarization of polarization control panel 50 in time with theprojection of the images such that left eye images are polarized one wayand right eye images are polarized in another way.

In the embodiment of FIG. 4 spatial modulator 20 may conveniently be apolarizing modulator arranged such that an output polarization ofspatial modulator 20 is aligned with the input polarization ofpolarization control panel 50. In some embodiments spatial modulator 20serves the dual roles of modulating brightness to compensate for lensflare and switching polarization between left and right eye projections.Spatial modulator 20 may be configured to control brightness by rotatingpolarization in one sense during display of a left eye image androtating polarization in another sense during display of a right eyeimage.

Spatial modulator 20 is a reflective modulator in some embodiments. Insuch embodiments a light transmission path from lens 16 to screen 18 maybe folded. Spatial light modulator 20 may be flat but is not necessarilyflat. Spatial light modulator 20 is curved in some embodiments. Spatialmodulator 20 may be but is not necessarily parallel to screen 18.Spatial light modulator is tilted relative to screen 18 in someembodiments.

Where a component (e.g. a display, spatial modulator, projector, model,lens, software module, processor, assembly, device, circuit, etc.) isreferred to above, unless otherwise indicated, reference to thatcomponent (including a reference to a “means”) should be interpreted asincluding as equivalents of that component any component which performsthe function of the described component (i.e., that is functionallyequivalent), including components which are not structurally equivalentto the disclosed structure which performs the function in theillustrated exemplary embodiments of the invention.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” As used herein, the terms “connected,”“coupled,” or any variant thereof, means any connection or coupling,either direct or indirect, between two or more elements; the coupling ofconnection between the elements can be physical, logical, or acombination thereof. Additionally, the words “herein,” “above,” “below,”and words of similar import, when used in this application, shall referto this application as a whole and not to any particular portions ofthis application. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively. The word “or,” in reference to alist of two or more items, covers all of the following interpretationsof the word: any of the items in the list, all of the items in the list,and any combination of the items in the list.

The technology provided herein can be applied to systems other than theexample systems described above. The elements and acts of the variousexamples described above can be combined to provide further examples.

From the foregoing, it will be appreciated that specific examples ofsystems and methods have been described herein for purposes ofillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the invention. Those skilled inthe art will appreciate that certain features of embodiments describedherein may be used in combination with features of other embodimentsdescribed herein, and that embodiments described herein may be practisedor implemented without all of the features ascribed to them herein. Suchvariations on described embodiments that would be apparent to theskilled addressee, including variations comprising mixing and matchingof features from different embodiments, are within the scope of thisinvention.

What is claimed is:
 1. A projector, comprising: a first modulationdevice of a first type configured to produce a first type of modulationcausing a variable pattern of intensities on a second modulation deviceof a second type and configured to spatially modulate intensities of themodulated light; a controller comprising a light distribution modelconfigured to model the variable pattern of intensities on the secondmodulation device based on a simulation that operates with respect togroups of pixels of the first modulation device to determine how theywill illuminate a region of the image, and a correction mechanismconfigured to determine settings of the second modulator, wherein thefirst modulation device creates a portion of an image to be projected atan increased overbrightness greater than that called for incorresponding image data and the subsequent modulation device correctsfor the overbrightness to a level called for in the corresponding imagedata.
 2. The projector according to claim 1, wherein the correctionmechanism includes compensation for a lensing artifact contained thedistribution of light on the second modulator.
 3. The projectoraccording to claim 1, wherein resolutions and contrast of the first andsecond modulators are not the same.
 4. The projector according to claim1, wherein the projector is part of a projection system that projectsseparate images having different qualities onto a screen for viewing bya viewer wherein the separate images of different qualities combine toform an image intended to be perceived by the viewer.
 5. The projectoraccording to claim 4, wherein one of the images comprises a lowresolution image different from the other image which comprises a higherresolution image.
 6. The projector according to claim 1, wherein thecontroller is configured to utilize a point spread function and modelingto determine a brightness at the second modulation device and utilizethe brightness at the second modulation device to determine an amount ofmodulation performed by the second modulation device to produce aprojected image specified by the image data.